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Science Forum Index » Electronics - Misc Forum » Lead free solder - exposed in a UK national newspaper
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| N_Cook |
 Posted: Thu Apr 03, 2008 2:56 am |
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http://www.guardian.co.uk/technology/2008/apr/03/research.engineering
Within a whisker of failure
Removing lead from solder may seem a smart idea environmentally, but the
resulting microscopic growths called tin whiskers could be just as
problematic
* Kurt Jacobsen
* The Guardian,
* Thursday April 3 2008
* Article history
This article appeared in the Guardian on Thursday April 03 2008 on p1 of the
Technology news & features section. It was last updated at 00:05 on April 03
2008.
Tin whiskers
On April 17 2005, the Millstone nuclear generating plant in Connecticut shut
down when a circuit board monitoring a steam pressure line short-circuited.
In 2006, a huge batch of Swatch watches, made by the eponymous Swiss
company, were recalled at an estimated cost of $1bn (£500m). In both cases,
"tin whiskers" - microscopic growths of the metal from soldering points on a
circuit board - were blamed for causing the problems.
It's not the first time these mysterious growths have been blamed for
electronics failures. In 1998 the Galaxy IV communications satellite
sputtered out after just five years; engineers diagnosed its failure as due
to "whiskers".
The US military blamed them for malfunctioning F-15 radar systems and
misguided Phoenix and Patriot missiles. In 1986, the US Food and Drug
Administration recalled a number of pacemakers because of these same
whiskers. In fact, they've been known about since the 1940s, and happen with
cadmium and zinc, too: during the second world war, similar whiskers would
short the cadmium tuning capacitors in aircraft radios. A decade later,
tin-based relays in AT&T telephone switching centres were found to cause
shorts.
The solution to "whiskering"? Mix lead into the solder, as was done from the
1950s. Colin Hughes, a physicist who worked on the first British nuclear
bomb, told me that the whiskering problem never came up during his career.
But now the lead is gone, by legal mandate, and whiskers are back - causing
potential problems for us all.
Since 2006, lead has been banned from solder in the European Union under the
2003 Reduction of Hazardous Substance (RoHS) directive, which gave
manufacturers three years to phase out lead.
The logic seemed reasonable. Removing lead from petrol (where it was used to
prevent engine mistiming) brought clear environmental and health benefits,
taking a harmful chemical that can affect intelligence out of the
atmosphere. Removing lead from solder, the 37% lead, 63% tin alloy used to
join metal objects in everything from plumbing to circuit boards, was an
obvious next step to prevent it leaching into ground water from dumped items
in landfills.
Meanwhile, the US and Japan have also been moving to lead-free solders. It's
a huge shift; the US Environmental Protection Agency (EPA) estimates that
80m kilograms of lead solder was used worldwide in 2002. Environmental
groups have applauded the move. "In the US we've been surviving without lead
solder for many years," says Rick Hind, legislative director of Greenpeace's
toxics campaign. "With less exposure to lead we will all benefit by being
smarter and making safer and more durable products." (The US has not made
lead-free solder obligatory, but does offer tax benefits for doing so.)
But without lead to tame it, tin behaves oddly on circuit boards. Left
alone, tin plating, like cadmium and zinc, spontaneously generates
microscopic shreds of metal - about one to five microns in diameter, or less
than one-tenth as wide as a human hair - which push up from the base. If
they grow far enough to touch another current-carrying location, they'll
cause a short that can wreck the equipment while leaving barely any trace.
The cause is becoming clearer. "I believe the mechanism of whisker formation
is now understood: it is due to compressive stress - caused by, say,
diffusion of copper into the tin - being built up in the tin layer which
breaks through the tin oxide barrier layer [to the air]," says Steve Jones
of Circatex, in South Shields. Critics cite reports that solder
substitutes - pure tin, tin-zinc, tin-silver-copper - simply cannot match
the lead mixture for reliability, coverage ("wetting" terminals), and cost
(silver is especially pricey). Therefore, the US military, Nasa and medical
and high-level research equipment are exempt from what authorities view as
untrustworthy commercial components.
"I still use lead-tin solder - it works better," says John Ketterson, a
solid state physicist at Northwestern University in Illinois. He notes the
tradeoffs of "cost, materials, strength of the solder and all that" during
this mandated changeover, and that manufacturers "have to get an experience
base" with new processes.
{ snipped as lengthy }
Tin whiskers: coming to a PC near you?
· They can grow at ambient temperature and humidity, or in vacuum
· They can grow in steady or varying temperatures (though the latter may
encourage growth)
· Whiskers' tips are atom-sharp. They will push through any coating, given
time
· They are a prevalent cause, only now being identified, of many past
equipment failures
· One whisker can carry about 30mA - more than enough to cause havoc in
digital circuits
· Silver-tin-copper ("SAC") solder slows but doesn't stop whisker growth
· SAC solder has more environmental impact than the lead-tin version
· Older 37%-63% lead-tin solder mix merely deforms, reducing stress and
hence minimising whiskering
· Whiskers can grow indefinitely
Source: Howard Johnson, Signal Consulting
--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/ |
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| Arfa Daily |
| Posted: Thu Apr 03, 2008 4:10 am |
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Quote:
The logic seemed reasonable. Removing lead from petrol (where it was used
to
prevent engine mistiming) brought clear environmental and health benefits,
taking a harmful chemical that can affect intelligence out of the
atmosphere. Removing lead from solder, the 37% lead, 63% tin alloy used to
join metal objects in everything from plumbing to circuit boards, was an
obvious next step to prevent it leaching into ground water from dumped
items
in landfills.
Meanwhile, the US and Japan have also been moving to lead-free solders.
It's
a huge shift; the US Environmental Protection Agency (EPA) estimates that
80m kilograms of lead solder was used worldwide in 2002.
Isn't it funny how figures can be 'distorted' to make facts suit the
context. By saying "80m kilos", the EPA make it sound like a HUGE amount,
but put that into a more 'recognisable' form, and it becomes 80 thousand
tonnes, which is not nearly so contentious. Then further, take that only 37%
of that was actually lead, and you are down to 29.6 thousand tonnes. Now
compare that to the world's lead-acid battery usage, where recycling of the
end-of-life product to recover the lead, has been sucessfully in place for
years. At 30th tonnes, the potential environmental impact of the lead in
solder, even if you *did* dump it all in the ground, is minuscule.
As I've said before, I'm glad that the avionics industry refuse to use the
stuff. The day they do is the day I stop flying ...
Arfa |
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| Eeyore |
| Posted: Thu Apr 03, 2008 5:59 am |
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N_Cook wrote:
Quote: http://www.guardian.co.uk/technology/2008/apr/03/research.engineering
Within a whisker of failure
About time too.
Never mind the reduced reliability (see the ERA study) caused by lead-free
solder when equipment is exposed to vibration.
Graham |
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| TheM |
| Posted: Thu Apr 03, 2008 6:39 am |
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"Eeyore" <rabbitsfriendsandrelations@hotmail.com> wrote in message news:47F4B8A8.ADD69B04@hotmail.com...
Its good for the way economy works nowadays. Buy, buy, buy the crap
that dies or obsoletes every 2-3 years.
Mark |
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| N_Cook |
| Posted: Thu Apr 03, 2008 8:16 am |
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| Allodoxaphobia |
| Posted: Thu Apr 03, 2008 11:00 am |
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On Thu, 03 Apr 2008 09:10:10 GMT, Arfa Daily wrote:
Quote: At 30th tonnes, the potential environmental impact of the lead in
solder, even if you *did* dump it all in the ground, is minuscule.
And, where do these pin-heads think the lead came from, in the first place?
Jonesy |
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| Guest |
| Posted: Thu Apr 03, 2008 4:14 pm |
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On Apr 3, 6:00 pm, exray <radioex...@geemail.com> wrote:
Quote: Jay Ts wrote:
snip
I've used 'alternative' solder. I could live with it if need be.
It
handles differently but geez, I think the fumes would kill me
faster
than eating a pound of lead solder everyday at tea. I've never
heard
the proponents addressing the wicked fumes of the 'better' solder.
-Bill (63/37)
You mean the fumes from the flux. You don't believe you're breathing
solder vapors, do you? In the 40+ years I've been using solder, I
doubt I've used 5 lbs and I do quite a bit of soldering.
GG |
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| Eeyore |
| Posted: Thu Apr 03, 2008 6:24 pm |
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N_Cook wrote:
Not sure if that's the one I had to be honest but looks interesting.
Graham |
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| Jay Ts |
| Posted: Thu Apr 03, 2008 8:16 pm |
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Allodoxaphobia wrote:
Quote: Arfa Daily wrote:
At 30th tonnes, the potential environmental impact of the lead in
solder, even if you *did* dump it all in the ground, is minuscule.
And, where do these pin-heads think the lead came from, in the first
place?
It came from deep within the ground, in the form of lead ore,
which I think is much less of a health hazard than metallic lead
decomposing in a landfill and seeping into the water supply.
In Europe, there are places where the Romans smelted lead 2000
years ago, and 8" or so below the topsoil, the dirt is still so
toxic that health officials (in Britain at least) don't allow
people to dig there, even wearing protective gear.
BTW, I'm not a pinhead, just someone who cares about my health,
that of others and a quality environment for us to all live in.
I tried lead-free solder, and gave up on it, at least for prototyping.
I was feeling a little bad about returning to traditional solder,
until the OP posted the article. Thanks - I feel vindicated. I hope
that someday there is a better alternative to lead-based solder,
but evidently it hasn't happened yet.
Jay Ts
--
To contact me, use this web page:
http://www.jayts.com/contact.php |
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| William Sommerwerck |
| Posted: Thu Apr 03, 2008 8:32 pm |
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As I've said before... It isn't a matter of whether electronic equipment has
lead in it, but what happens to that equipment when it's disposed of. It's
the latter that should be considered. |
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| James Sweet |
| Posted: Thu Apr 03, 2008 8:49 pm |
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"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:ruednS26lvW_GGjanZ2dnUVZ_oWdnZ2d@comcast.com...
Quote: As I've said before... It isn't a matter of whether electronic equipment
has
lead in it, but what happens to that equipment when it's disposed of. It's
the latter that should be considered.
And lead isn't the only toxic substance used in electronic equipment and the
process used to manufacture it.
Is a lead-free item that fails and ends up in the landfill after 2 years
better than a lead-containing device that lasts a decade? |
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| exray |
| Posted: Thu Apr 03, 2008 9:00 pm |
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Jay Ts wrote:
Quote:
In Europe, there are places where the Romans smelted lead 2000
years ago, and 8" or so below the topsoil, the dirt is still so
toxic that health officials (in Britain at least) don't allow
people to dig there, even wearing protective gear.
Welcome to California.
Quote:
I tried lead-free solder, and gave up on it, at least for prototyping.
I was feeling a little bad about returning to traditional solder,
until the OP posted the article. Thanks - I feel vindicated. I hope
that someday there is a better alternative to lead-based solder,
but evidently it hasn't happened yet.
I've used 'alternative' solder. I could live with it if need be. It
handles differently but geez, I think the fumes would kill me faster
than eating a pound of lead solder everyday at tea. I've never heard
the proponents addressing the wicked fumes of the 'better' solder.
-Bill (63/37)
--
Posted via a free Usenet account from http://www.teranews.com |
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| Eeyore |
| Posted: Thu Apr 03, 2008 9:21 pm |
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William Sommerwerck wrote:
Quote: As I've said before... It isn't a matter of whether electronic equipment has
lead in it, but what happens to that equipment when it's disposed of. It's
the latter that should be considered.
AIUI, lead in metallic form is pretty stable and doesn't 'leach' into
groundwater the way some would have us believe.
Graham |
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| exray |
| Posted: Thu Apr 03, 2008 10:13 pm |
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stratus46@yahoo.com wrote:
Quote:
You mean the fumes from the flux. You don't believe you're breathing
solder vapors, do you? In the 40+ years I've been using solder, I
doubt I've used 5 lbs and I do quite a bit of soldering.
GG
I've never turned on my shop spectrometer to determine if it was the
flux or solder. I just know that the new stuff doesn't smell as
friendly to my human nose.
40+ years, 5 pounds, yadda,yadda...how much 'new' solder have you used?
I suspect you're just trying to pick a fight. I'm not playing. See ya.
-ex
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Posted via a free Usenet account from http://www.teranews.com |
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| Jay Ts |
| Posted: Thu Apr 03, 2008 10:42 pm |
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William Sommerwerck wrote:
Quote: As I've said before... It isn't a matter of whether electronic equipment
has lead in it, but what happens to that equipment when it's disposed
of. It's the latter that should be considered.
There's the other end of the process too: mining, smelting,
and the rest of the manufacturing process that might be producing
pollution. All that is outside my realm of knowledge. Maybe they
do it in an "environmentally-friendly" manner these days? I really
have no idea.
I think ideally, we'd find something better to use, but although
it's gotten a lot of bad press, there are much worse things than
lead. Such as other heavy metals, notably cadmium and mercury.
Another source of lead is CRTs, many of which are still in use.
They contain about 5 pounds of lead each for radiation protection,
quite a bit more than is contained in the solder in the PC boards.
And the replacements, flat screen monitors, have mercury in
the fluorescent backlights.
I've had trouble with mercury poisoning in the past, but even
though I'd been exposed to a lot of lead as a child, I've never
discerned any problem from it. (It's tricky though, low- to
moderate-level heavy metal poisoning can easily go unnoticed,
while causing significant health problems.)
This does not mean that solder-containing lead is "good",
just that it's appropriate to keep things in perspective.
Jay Ts
--
To contact me, use this web page:
http://www.jayts.com/contact.php |
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